From Northwoods Explorer http://www.geocaching.com/seek/cache_details.aspx?wp=gc106vgLandslides in North America cause approximately $5 billion dollars per year in damage, and kill between 40 and 75 people annually. The casualties are primarily caused by rockfalls, rock slides, and debris flows.
This earthcache will give you a first hand look at the damage that a landslide can do to the environment. Imagine if this landslide had taken place in a populated area. The 1970 Simon and Garfunkel song titled "Bridge Over Troubled Waters" which was followed by the 1977 Paul Simon song, "Slip Sliding Away," describe this area. While these songs had nothing to do with this landslide it make for an interesting comparison.
Some slopes are susceptible to landslides, whereas others are more stable. Many factors contribute to the instability of slopes, but the main controlling factors are the nature of the underlying bedrock and soil, the configuration of the slope, the geometry of the slope, and ground-water conditions. Once a landslide is triggered, material is transported by various mechanisms including sliding, flowing, and falling. Landslides often occur along planes of weakness that may parallel the hill slope. Soils such as silt and clay are weaker than rock and commonly have complex or multiple planes of weakness. Landslides occur in slopes oversteepened by the process of stream erosion or by the activities of man in grading slopes. In many instances oversteepened slopes stand in apparent stability until abnormally high ground-water conditions occur, thus reducing the shear resistance and triggering the landslide. Once a slope in a sensitive soil has been oversteepened by erosion at the toe or by excavation work and the ground-water table is high, the stage is set for a landslide to occur.
Three distinct physical events occur during a landslide: the initial slope failure, the subsequent transport, and the final deposition of the slide materials. Landslides can be triggered by gradual processes such as weathering or by external mechanisms or even a combination of factors. This type of slide is called a rotational slide. Where the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide. It was caused by a combination of factor going back to the last ice age where as it retreated it left a fine layer of clay that covered the region. The fact that the water was high for several years cause the gradual undercutting of the river bank which when coupled with heavy spring rainfall and run off cause the bank to fail. The area above the slide had been recently logged which changed the general nature of the spring run off. The heavy rainfall induced increased erosion and oversteepening of the slope. Besides this, the increased rainfall raised the water table, which increased the pore water pressure, which in turn reduced the shear resistance in the glacial marine clay causing it to liquefy and finally slide.
DO NOT ATTEMPT TO ACCESS THIS CACHE FROM THE TRANS CANADA HIGHWAY. This earthcache can be located by using an access road off the Canterbury Exit. Just drive to the end of the access road where it turns into an ATV trail from here either follow the ATV trail or your GPS to the location.
At the coordinates listed above you will be in the general area of the crown or top of the slide looking toward the river. To log this Earthcache: Post a photo of you and your GPS and then send an email to me through my profile with the following information: What is the height of the main scarp at the slide's crown. Use the diagram below to identify the parts of the slide. Please begin your email with the name of the earthcache and make sure your log includes the number of people in your group.
If you would like to explore the slide access is easiest along the upstream edge of the slide, do not attempt to access the slide from the top. For further information you might what to read: "Landslide Types and Process" USGS Fact Sheet 2004-3072 July 2004 http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html
From Northwoods Explorer http://www.geocaching.com/seek/cache_details.aspx?wp=gc106vgLandslides in North America cause approximately $5 billion dollars per year in damage, and kill between 40 and 75 people annually. The casualties are primarily caused by rockfalls, rock slides, and debris flows.
This earthcache will give you a first hand look at the damage that a landslide can do to the environment. Imagine if this landslide had taken place in a populated area. The 1970 Simon and Garfunkel song titled "Bridge Over Troubled Waters" which was followed by the 1977 Paul Simon song, "Slip Sliding Away," describe this area. While these songs had nothing to do with this landslide it make for an interesting comparison.
Some slopes are susceptible to landslides, whereas others are more stable. Many factors contribute to the instability of slopes, but the main controlling factors are the nature of the underlying bedrock and soil, the configuration of the slope, the geometry of the slope, and ground-water conditions. Once a landslide is triggered, material is transported by various mechanisms including sliding, flowing, and falling. Landslides often occur along planes of weakness that may parallel the hill slope. Soils such as silt and clay are weaker than rock and commonly have complex or multiple planes of weakness. Landslides occur in slopes oversteepened by the process of stream erosion or by the activities of man in grading slopes. In many instances oversteepened slopes stand in apparent stability until abnormally high ground-water conditions occur, thus reducing the shear resistance and triggering the landslide. Once a slope in a sensitive soil has been oversteepened by erosion at the toe or by excavation work and the ground-water table is high, the stage is set for a landslide to occur.
Three distinct physical events occur during a landslide: the initial slope failure, the subsequent transport, and the final deposition of the slide materials. Landslides can be triggered by gradual processes such as weathering or by external mechanisms or even a combination of factors. This type of slide is called a rotational slide. Where the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide. It was caused by a combination of factor going back to the last ice age where as it retreated it left a fine layer of clay that covered the region. The fact that the water was high for several years cause the gradual undercutting of the river bank which when coupled with heavy spring rainfall and run off cause the bank to fail. The area above the slide had been recently logged which changed the general nature of the spring run off. The heavy rainfall induced increased erosion and oversteepening of the slope. Besides this, the increased rainfall raised the water table, which increased the pore water pressure, which in turn reduced the shear resistance in the glacial marine clay causing it to liquefy and finally slide.
DO NOT ATTEMPT TO ACCESS THIS CACHE FROM THE TRANS CANADA HIGHWAY. This earthcache can be located by using an access road off the Canterbury Exit. Just drive to the end of the access road where it turns into an ATV trail from here either follow the ATV trail or your GPS to the location.
At the coordinates listed above you will be in the general area of the crown or top of the slide looking toward the river. To log this Earthcache: Post a photo of you and your GPS and then send an email to me through my profile with the following information: What is the height of the main scarp at the slide's crown. Use the diagram below to identify the parts of the slide. Please begin your email with the name of the earthcache and make sure your log includes the number of people in your group.